1. Field of the Invention
The present invention relates to an ink jet printer for completing printing of data in a printing medium by moving the printing medium without moving a printing head.
2. Description of the Related Art
In recent years, an ink jet printer (hereafter referred to as line-head-type ink jet printer) is practically used which has a line-type printing head (hereafter referred to as line head) in which many nozzles are arranged over the width or more of a printing medium from a request for increase in the printing speed of an ink jet printer for discharging ink from a nozzle so as to print data in a printing medium.
In the case of this line-head-type ink jet printer, the face of a printing medium on which data will be printed is continuously or intermittently conveyed by facing a face on which the nozzle of a line head is formed. Moreover, the line head selectively discharges ink in accordance with the information to be printed out of many arranged nozzles toward the face of the conveyed printing medium on which data will be printed. That is, the line-head-type ink jet printer completes a data printing in a printing medium only by moving a printing medium in one direction without moving a printing head.
In the case of the line-head-type printer, a configuration is known in which data is printed in a printing medium conveyed by being adsorbed by a conveying belt which is applied between a pair of rollers as disclosed in JP10-202922A.
Moreover, in the case of the printing head of an ink-jet-type printer not applied only to the line type, the solvent of ink is evaporated from a nozzle from which ink drips are discharged which results in the rising of the viscosity of the ink in the nozzle. In the worst case, the ink is solidified or foreign matter enters the nozzle and the nozzle is clogged, and the performance for discharging ink drips from the nozzle may be deteriorated. Therefore, the ink jet printer performs clogging prevention discharge by discharging ink drips independently of printing to prevent clogging before the discharge performance is deteriorated due to the rising of the ink viscosity in the nozzle or the clogging of the nozzle, and is constituted so that preferable printing quality is maintained.
In the case of the above line-head-type ink jet printer, as disclosed in JP2001-113690A, a technique is known which, even if continuously printing data in many printing media, avoids that the clogging prevention discharge lengthens the time up to completion of printing by forming a plurality of holes in a conveying belt applied between a pair of conveying rollers to convey a printing medium and by discharging ink drips through the holes.
Moreover, in the case of the printing head of an ink jet printer not applied only to the line type, the solvent of ink is evaporated from a nozzle for discharging ink drips and the ink in the nozzle is solidified foreign matter gets into the nozzle to clog it, thereby, the performance for discharging ink drips may be deteriorated. Therefore, the ink jet printer is constituted by having a protective cap for covering the nozzle face to protect the nozzle face, preventing the solvent from vaporizing foreign matter from entering the nozzle, and for preventing from clogging of the nozzle so that preferable printing quality is maintained.
For the above line-head-type ink jet printer, a technique is conventionally known which evacuates a cap to the side of a conveying belt, moves a printing head set on the conveying belt upward forming a gap between the printing head and the conveying belt, and inserts the cap into the gap from the direction orthogonal to the conveying direction of the conveying belt as disclosed in JP2002-120386A.
Moreover, in the case of the printing head of an ink jet printer, the solvent of ink is evaporated from the nozzle for discharging ink drips and the ink in the nozzle is solidified or foreign matter enters the nozzle and thus the nozzle is clogged and thereby, the performance for discharging ink drips from the nozzle may be deteriorated. Therefore, the ink jet printer has a discharge performance recovery apparatus for recovering the deteriorated discharge performance and is constituted so that preferable printing quality is maintained.
For the above line-head-type ink jet printer, a technique is known which rotates a line head to a no-printing area which is an area in which a nozzle does not face a printing medium on a plane parallel with the printing medium to recover the discharge performance of the line head as disclosed in JP2002-103638A.
Moreover, in the case of the above line-head-type ink jet printer, a configuration is known which conveys a printing medium by mounting the printing medium on a conveying belt applied between a pair of conveying rollers as disclosed in JP8-132700A. Furthermore, a configuration is known in which a spur is applied between printing heads in the conveying direction of the printing medium to prevent from floating the printing medium being conveyed from a conveying belt.
However, in the case of the configuration disclosed in JP10-202922A, the conveying speed of a printing medium is fluctuated due to the telescopic motion of a conveying belt or the interval between a printing head and the printing medium becomes unstable because the conveying belt vibrates between conveying rollers and thereby, the landing position of ink drips on the printing medium maybe shifted from a predetermined position. The landing position shift of ink drips due to these phenomena more remarkably occurs as the conveying interval by the conveying belt increases. That is, there is an unsolved problem that it is difficult to lengthen the conveying interval by a conveying belt while maintaining a preferable printing quality.
The present invention is made to solve the above problem and its first object is to provide an ink jet printer capable of lengthening the conveying interval by a conveying belt without spoiling the printing quality, further improving the printing quality, and increasing in the printing speed.
In the case of the configuration disclosed in JP10-202922A, many nozzles for discharging ink drips are arranged over the A4 minor dimension in the sheet width direction. Moreover, a conveying belt has a width longer than a nozzle string which is constituted of many arranged nozzles and is so set as to face the nozzles in order to cover the nozzle string.
Therefore, when applying non-marginal printing to an A4-size printing sheet, ink outgoing from the printing area of the printing sheet contaminates a conveying belt. Moreover, there is an unsolved problem that it is difficult to apply non-marginal printing to a printing sheet having a size smaller than size A4 or a different shape.
The present invention is made to solve the above problem and its second object is to provide an ink jet printer making it possible to apply non-marginal printing to the printing medium having various dimensions and shapes without contaminating a conveying belt with ink.
In the case of the prior art disclosed in JP2001-113690A, it is necessary to form holes on a conveying belt for conveying a printing medium. When applying a predetermined tensile load to the conveying belt on which holes are formed, a tensile stress and strain are increased in portions nearby the holes compared to other portions. That is, the tensile stress and strain are ununiformly generated on the entire perimeter of the conveying belt because of the holes which are formed upon.
This is not preferable for an ink jet printer for printing data in a printing medium by conveying the printing medium through a conveying belt in the point that it is difficult to improve the printing quality. That is, in the case of conveying by the conveying belt, the conveying speed of the printing medium is fluctuated due to the telescopic motion of the conveying belt or due to the conveying belt vibrates between conveying rollers and thereby, the interval between a printing head and the printing medium becomes unstable and the landing position of ink drips on the printing medium is shifted from a predetermined position.
That is, in the case of the prior art disclosed in the above JP2001-113690A, by forming holes on a conveying belt, there are unsolved problems that fluctuation of the conveying speed and vibration of the conveying belt are encouraged which makes it difficult to improve the printing quality.
The present invention is made to solve the above problems and its third object is to provide an ink jet printer for restraining the fluctuation of the conveying speed of a printing medium and for making it possible to realize clogging prevention discharge without deteriorating the printing quality and printing speed.
Moreover, in the case of the prior art disclosed in the above JP2002-120386A, a configuration is used in which a printing head is moved upward and a cap is moved under the printing head from the side. Therefore, it is difficult to decrease the time until a protective cap is set to a printing head and the time until the protective cap is removed from the printing head and evacuated. Moreover, a mechanism for moving the printing head and the protective cap is necessary. Therefore, there are unsolved problems that it is difficult to maintain a high reliability of a mechanism portion and to decrease the number of components.
The present invention is made to solve the above problems and its fourth object is to provide an ink jet printer having a simple configuration and capable of decreasing the time required for setting or removing a protective cap to or from a printing head and of securing a high reliability.
Moreover, in the case of the prior art disclosed in the above JP2002-103638A, it is limited to increase the rotational speed without damaging a line head, thus it is difficult to decrease the time required for recovering the discharge performance, and a mechanism and control for rotation become complex. Furthermore, because a discharge performance recovery apparatus must be set in a non-printing area, there are unsolved problems that downsizing is difficult and the like.
The present invention is made to solve the above problem and its fifth object is to provide an ink jet printer for decreasing the time to be required for recovering the discharge performance, and for being easily downsized.
Moreover, in the case of the prior art disclosed in the above JP8-132700A, a spur to restrain a printing medium to be lifted while transporting is set between printing heads in the conveying direction of a printing medium. Therefore, the lift is restrained by the spur for a printing medium having a high rigidity such as label paper and it is possible to preferably keep the interval between the printing head and the printing medium. However, a sufficient effect cannot be obtained for a warp produced as ink infiltrates into a printing medium which has a low rigidity such as a printing sheet.
That is, as shown in FIGS. 52A to 52D which are the illustrations for explaining a problem of the prior art, in the case of a printing sheet P, when the ink IK discharged from a printing head HDA infiltrates into a printing face PP, the balance between the printing face PP and a conveying face PH which is an opposite face to the printing face PP is broken at a portion where the ink IK infiltrates and a warp is produced (FIG. 52B).
When the printing sheet P mounted on a conveying belt V is conveyed and reaches a spur portion, the warp of the printing sheet P is corrected by a spur SP as shown in FIG. 52C.
When the printing sheet P passes through the spur portion and reaches the printing head HDB, a warp is produced again on the printing sheet P because there is not an object for correcting the warp as shown in FIG. 52D. That is, though the warp of the printing sheet P is temporarily corrected at the spur portion, the warp is produced again after passing through the spur portion and an unsolved problem remains that it is difficult to properly keep the interval between the printing head and the printing sheep P.
The present invention is made to solve the above problem and its sixth object is to provide an ink jet printer capable of restraining the lift of a printing medium and properly keeping the interval between the printing medium and a printing head.